I want to use ArcGIS 10.1 to calculate the straight (euclidean) distances from zip codes to their nearest city centers in about 300 U.S. metropolitan areas. I have two point shpfiles: one includes the centroids of all zip codes and the other includes the points that represent city centers. Both of the two shpfiles are in the GCS_North_American_1983, which prohibits me from doing the distance calculation.

I have converted the GCS into North America Lambert Conformal Conic to do the calculation. It worked. But I am not sure whether this is the best way to do it. Any advice is appreciated!

Welcome to GIS-SE! Would you be able to edit your question and tags to specify what GIS software and version you are using, please? It looks like ArcGIS for Desktop but I prefer not to assume that.
– PolyGeo♦Nov 21 '13 at 1:15

4

You also might like to say what you mean by distance. Do you mean "across the surface of the earth" (and if so, what do you mean by surface - geoid, ellipsoid, actual terrain), or "along some roads" or "really straight line even if that goes through the surface".
– BradHardsNov 21 '13 at 3:24